[PDF] Useful Python Libraries for Network Engineers

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Hank Preston, ccie38336 R/S

Developer Advocate, DevNet

Season 1, Talk 1

Useful Python Libraries for Network

Engineers

Twitter: @hfpreston

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Libraries to Work with Data

API Libraries

Configuration Management

Tools and Libraries

Some Other Cool Python Stuff

What are we going to talk about?

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Libraries to Work with Data

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

XML -xmltodict

pip install xmltodict import xmltodict JSON import json

YAML -PyYAML

pip install PyYAML import yaml CSV import csv

YANG -pyang

import pyang

Manipulating Data of All Formats

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Easily work with XML data

Convert from XML -> Dict*

and back xmltodict.parse(xml_data) xmltodict.unparse(dict)

Python includes a native

Markup(html/xml) interfaces

as well

More powerful, but also more

complex * Technically to an OrderedDict # Import the xmltodict library importxmltodict # Open the sample xml file and read it into variable withopen("xml_example.xml") asf: xml_example = f.read() # Print the raw XML data print(xml_example) # Parse the XML into a Python dictionary xml_dict = xmltodict.parse(xml_example) # Save the interface name into a variable using XML nodes as keys int_name = xml_dict["interface"]["name"] # Print the interface name print(int_name) # Change the IP address of the interface xml_dict["interface"]["ipv4"]["address"]["ip"] = "192.168.0.2" # Revert to the XML string version of the dictionary print(xmltodict.unparse(xml_dict))

Treat XML like Python Dictionaries with xmltodict

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

JSON and Python go

together like peanut butter and jelly json.loads(json_data) json.dumps(object)

JSON Objects convert to

Dictionaries

JSON Arrays convert to

Lists # Import the jsontodictlibrary import json # Open the sample jsonfile and read it into variable with open("json_example.json") as f: json_example= f.read() # Print the raw jsondata print(json_example) # Parse the jsoninto a Python dictionary json_dict= json.loads(json_example) # Save the interface name into a variable int_name= json_dict["interface"]["name"] # Print the interface name print(int_name) # Change the IP address of the interface json_dict["interface"]["ipv4"]["address"][0]["ip"] = \ "192.168.0.2" # Revert to the jsonstring version of the dictionary print(json.dumps(json_dict))

To JSON and back again with json

# Import the jsontodictlibrary importjson # Open the sample jsonfile and read it into variable withopen("json_example.json") asf: json_example= f.read() # Print the raw jsondata print(json_example) # Parse the jsoninto a Python dictionary json_dict= json.loads(json_example) # Save the interface name into a variable int_name= json_dict["interface"]["name"] # Print the interface name print(int_name) # Change the IP address of the interface json_dict["interface"]["ipv4"]["address"][0]["ip"] = \ "192.168.0.2" # Revert to the jsonstring version of the dictionary print(json.dumps(json_dict)) © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Easily convert a YAML file

to a Python Object yaml.load(yaml_data) yaml.dump(object)

YAML Objects become

Dictionaries

YAML Lists become Lists

# Import the yamltodictlibrary import yaml # Open the sample yamlfile and read it into variable with open("yaml_example.yaml") as f: yaml_example= f.read() # Print the raw yamldata print(yaml_example) # Parse the yamlinto a Python dictionary yaml_dict= yaml.load(yaml_example) # Save the interface name into a variable int_name= yaml_dict["interface"]["name"] # Print the interface name print(int_name) # Change the IP address of the interface yaml_dict["interface"]["ipv4"]["address"][0]["ip"] = \ "192.168.0.2" # Revert to the yamlstring version of the dictionary print(yaml.dump(yaml_dict, default_flow_style=False))

YAML? Yep, Python Can Do That Too!

# Import the yamltodictlibrary importyaml # Open the sample yamlfile and read it into variable withopen("yaml_example.yaml") asf: yaml_example= f.read() # Print the raw yamldata print(yaml_example) # Parse the yamlinto a Python dictionary yaml_dict= yaml.load(yaml_example) # Save the interface name into a variable int_name= yaml_dict["interface"]["name"] # Print the interface name print(int_name) # Change the IP address of the interface yaml_dict["interface"]["ipv4"]["address"][0]["ip"] = \ "192.168.0.2" # Revert to the yamlstring version of the dictionary print(yaml.dump(yaml_dict, default_flow_style=False)) © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Treat CSV data as lists

csv.reader(file_object)

Efficiently processes large

files without memory issues

Options for header rows

and different formats # Import the csv library importcsv # Open the sample csv file and print it to screen withopen("csv_example.csv") asf: print(f.read()) # Open the sample csv file, and create a csv.reader object withopen("csv_example.csv") asf: csv_python= csv.reader(f) # Loop over each row in csv and leverage the data # in code forrow incsv_python: print("{device} is in {location} "\ "and has IP {ip}.".format( device = row[0], location = row[2], ip= row[1]

Import Spreadsheets and Data with csv

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Modulethat is a self-contained

top-level hierarchy of nodes

Usescontainersto group related

nodes

Liststo identify nodes that are

stored in sequence

Each individual attribute of a node

is represented by aleaf

Every leaf must have an

associatedtype module ietf-interfaces { import ietf-yang-types { prefix yang; container interfaces { list interface { key "name"; leaf name { type string; leaf enabled { type boolean; default "true";

YANG Data Modeling Language -IETF Standard

Example edited for simplicity and brevity

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Working in native YANG can be

challenging pyangis a Python library for validating and working with

YANG files

Excellent for network

developers working with

NETCONF/RESTCONF/gRPC

Quickly understand the key

operational view of a model echo "Print the YANG module in a simple text tree" pyang-f tree ietf-interfaces.yang echo "Print only part of the tree" pyang-f tree --tree-path=/interfaces/interface \ ietf-interfaces.yang echo "Print an example XML skeleton (NETCONF)" pyang-f sample-xml-skeleton ietf-interfaces.yang echo "Create an HTTP/JS view of the YANG Model" pyang-f jstree-o ietf-interfaces.html\ ietf-interfaces.yang open ietf-interfaces.html echo 'Control the "nested depth" in trees' pyang-f tree --tree-depth=2 ietf-ip.yang echo "Include deviation models in the processing" pyang-f tree \ ietf-ip.yang

Investigate YANG Models with pyang

data_manipulation/yang/pyang-examples.sh © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

API Libraries

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

REST APIs ²requests

pip install requests import requests

NETCONF ²ncclient

pip install ncclient import ncclient

Network CLI ²netmiko

pip install netmiko import netmiko

SNMP ²PySNMP

pip install pysnmp import pysnmp

Access Different APIs Easily

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Full HTTP Client

Simplifies authentication,

headers, and response tracking

Great for REST API calls, or any

HTTP request

Network uses include

RESTCONF, native REST APIs,

JSON-RPC

0MNH +773 FMOOV RLPO (MVH XVLQJ ´UHTXHVPVµ

http://docs.python-requests.org © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Example: Retrieving

Configuration Details with

RESTCONF

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Import libraries importrequests, urllib3 importsys # Add parent directory to path to allow importing common vars sys.path.append("..") # noqa fromdevice_infoimportios_xe1 asdevice # noqa # Disable Self-Signed Cert warning for demo # Setup base variable for request restconf_headers= {"Accept": "application/yang-data+json"} restconf_base= "https://{ip}:{port}/restconf/data" interface_url= restconf_base+ "/ietf-interfaces:interfaces/interface={int_name}"

RESTCONF: Basic Request for Device Data 1/2

device_apis/rest/restconf_example1.pyCode edited for display on slide © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Create URL and send RESTCONF request to core1 for GigE2 Config url= interface_url.format(ip= device["address"], port = device["restconf_port"], int_name= "GigabitEthernet2" r = requests.get(url, headers = restconf_headers, auth=(device["username"], device["password"]), verify=False) # Print returned data print(r.text) # Process JSON data into Python Dictionary and use interface = r.json()["ietf-interfaces:interface"] print("The interface {name} has ipaddress {ip}/{mask}".format( name = interface["name"], ip= interface["ietf-ip:ipv4"]["address"][0]["ip"], mask = interface["ietf-ip:ipv4"]["address"][0]["netmask"],

RESTCONF: Basic Request for Device Data 2/2

device_apis/rest/restconf_example1.pyCode edited for display on slide © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Example: Updating

Configuration with

RESTCONF

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Setup base variable for request restconf_headers["Content-Type"]= "application/yang-data+json" # New Loopback Details loopback = {"name": "Loopback101", "description": "Demo interface by RESTCONF", "ip": "192.168.101.1", "netmask": "255.255.255.0"} # Setup data body to create new loopback interface data = { "ietf-interfaces:interface": { "name": loopback["name"], "description": loopback["description"], "type": "iana-if-type:softwareLoopback", "enabled": True, "ietf-ip:ipv4": { "address": [ {"ip": loopback["ip"], "netmask": loopback["netmask"]}

RESTCONF: Creating a New Loopback 1/2

device_apis/rest/restconf_example2.pyOnly showing significant code changes © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Create URL and send RESTCONF request to core1 for GigE2 Config url= interface_url.format(ip= core1_ip, int_name= loopback["name"]) r = requests.put(url, headers = restconf_headers, auth=(username, password), json= data, verify=False) # Print returned data print("Request Status Code: {}".format(r.status_code))

RESTCONF: Creating a New Loopback 2/2

device_apis/rest/restconf_example2.pyOnly showing significant code changes © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Full NETCONF Manager (ie

client) implementation in Python

See later presentation on

NETCONF details

Handles all details including

authentication, RPC, and operations

Deals in raw XML

Easily Interface with NETCONF and ncclient

https://ncclient.readthedocs.io © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Example: Retrieving

Configuration Details with

NETCONF

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Import libraries fromncclientimportmanager importxmltodict # Create filter template for an interface interface_filter= """ {int_name}

NETCONF: Basic Request for Device Data 1/2

device_apis/netconf/netconf_example1.pyCode edited for display on slide © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Open NETCONF connection to device withmanager.connect(host=core1_ip, username=username, password=password, hostkey_verify=False) asm: # Create desired NETCONF filter and filter= interface_filter.format(int_name= "GigabitEthernet2") r = m.get_config("running", filter) # Process the XML data into Python Dictionary and use interface = xmltodict.parse(r.xml) interface = interface["rpc-reply"]["data"]["interfaces"]["interface"] print("The interface {name} has ipaddress {ip}/{mask}".format( name = interface["name"]["#text"], ip= interface["ipv4"]["address"]["ip"], mask = interface["ipv4"]["address"]["netmask"],

NETCONF: Basic Request for Device Data 2/2

device_apis/netconf/netconf_example1.pyCode edited for display on slide © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

Example: Updating

Configuration with

NETCONF

© 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # Create config template for an interface config_data= """ {int_name} {description} ianaift:softwareLoopback true

{ip} {netmask}

NETCONF: Creating a New Loopback 1/2

device_apis/netconf/netconf_example2.pyOnly showing significant code changes © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public # New Loopback Details loopback = {"int_name": "Loopback102", "description": "Demo interface by NETCONF", "ip": "192.168.102.1", "netmask": "255.255.255.0"} # Open NETCONF connection to device withmanager.connect(host=core1_ip, username=username, password=password, hostkey_verify=False) asm: # Create desired NETCONF config payload and config = config_data.format(**loopback) r = m.edit_config(target = "running", config = config) # Print OK status print("NETCONF RPC OK: {}".format(r.ok))

NETCONF: Creating a New Loopback 2/2

device_apis/netconf/netconf_example2.pyOnly showing significant code changes © 2018 Cisco and/or its affiliates. All rights reserved. Cisco Public

If no other API is available"

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